1. Field of the Invention
The present invention relates generally to the field of heat exchange apparatus and more specifically to methods and apparatuses of cleaning these heat exchange devices.
2. Description of the Prior Art
Examples of pertinent patents are U.S. Pat. Nos. 3,130,778; 3,291,197; 3,369,598; 3,919,732 and Belgian Pat. No. 525,076.
Belgian Pat. No. 525,076 shows horizontally mounted heat exchange tubes. Elastic floating balls having a diameter equal to the interior diameter of the heat exchange tubes, abrade the interior walls of the tubes. The balls circulate by means of a pump which continually pushes balls through the holes of the tubes. A large pipe traps the floating balls and returns them to the pump for continuous cleaning of the tubes.
U.S. Pat. No. 3,919,732 shows a descaling system for condenser cooling tubes. Sponge balls are forced through cooling tubes by a three-switch valve capable of drawing out used descaling elements and introducing fresh descaling elements into the descaling line. A wire net disposed above the holder for the sponge balls prevents the balls from escaping from the holder.
U.S. Pat. No. 3,369,598 shows a heat exchanger having a filling of rolling bodies. A cylindrical housing is divided by plates into individual chambers and filled with rolling bodies. The rolling bodies are set into motion by rotation of the cylinder. The interior movement of the bodies against the cylinder cleans the surfaces of the cylinder. In addition the rolling bodies may be removed from the interior of the cylinder to effect movement outside the cylinder.
U.S. Pat. Nos. 3,130,778 and 3,291,197 show shot cleaning systems for heat exchangers. A recovery hopper means above the surfaces to be cleaned discharges steel shots onto the interior surfaces of the heat exchanger. After passing through the area to be cleaned the shots settle into a collection hopper. Pneumatic conveying means in U.S. Pat. No. 3,130,778 return the shots upward to the recovery hopper. Hydraulic pressure in U.S. Pat. No. 3,291,197 conveys shots upward to the recovery hopper means.
The present invention is a new and different apparatus and method for cleaning heat exchangers. Although some prior art, for example U.S. Pat. No. 3,919,732 and Belgian Pat. No. 525,076 show floating balls which abrade the surfaces of the heat exchange tubes, none has appendages trailing from them as does the present invention to increase the randomness of deflection of the balls against the tubes. As a result in prior art the floating bodies tend to clean in a more predictable pattern neglecting the cleaning of parts of the tube while over cleaning other parts. This increases the wear on parts of the tubes and allows sludge to build up on other parts of the tubes. Eventually uneven cleaning of the tubes contributes to an increasing lack of efficiency to exchange heat by the tubes. The fusiform shape of the floating bodies of the present invention further aids in making the movement of the floating bodies more erratic so that they will be more likely to clean all parts of the tubes.
The asymmetrical orientation of the tubes, mounted angularly to one another further increases the random movement of the floating bodies. This orientation causes the seawater flowing across the exterior of the tubes to vary in velocity due to different tube densities from area to area. The varying seawater flow allows the floating bodies to simultaneously rise and sink in the flow abrading both upper and lower surfaces of the heat exchange tubes.
None of the prior art shows tubes mounted asymmetrically, nor does any show varying seawater velocity flows.
The present invention may be adapted to clean a variety of heat exchange tubes depending upon the material from which the tubes were constructed. The floating objects of the present invention may be encased in whatever material which maximizes cleaning of marine fouling from the heat exchange tube but minimizes the wear on the material of the heat exchange tubes. None of the prior art demonstrates the flexibility of use of the present invention.
A significant new approach taken by the present invention is to clean the exterior surfaces of the heat exchange tubes. The prior art concentrates on cleaning the interior surfaces of the heat exchange tubes. The present invention directs its attention towards the exterior surfaces because poor thermal conductivity will result from fouled exterior surfaces as well as from fouled interior surfaces.
The present invention has protective screens which prevent the floating objects from escaping the area to be cleaned. The holes of the screen are large enough to permit worn floating bodies to pass through them so they can be easily removed. None of the prior art shows screens for keeping the floating bodies in the cleaning area. None of the prior art shows as simple a method of removing worn bodies as the present invention, as worn bodies are generally siphoned off by a valve means in prior art disclosures.